LibJS: Rename Environment Records so they match the spec :^)

This patch makes the following name changes:

- ScopeObject => EnvironmentRecord
- LexicalEnvironment => DeclarativeEnvironmentRecord
- WithScope => ObjectEnvironmentRecord

Userland/Libraries/LibJS/Runtime/EnvironmentRecord.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+struct Variable {
+    Value value;
+    DeclarationKind declaration_kind;
+};
+
+class EnvironmentRecord : public Object {
+    JS_OBJECT(EnvironmentRecord, Object);
+
+public:
+    virtual Optional<Variable> get_from_scope(const FlyString&) const = 0;
+    virtual void put_to_scope(const FlyString&, Variable) = 0;
+    virtual bool delete_from_scope(FlyString const&) = 0;
+    virtual bool has_this_binding() const = 0;
+    virtual Value get_this_binding(GlobalObject&) const = 0;
+
+    EnvironmentRecord* parent() { return m_parent; }
+    const EnvironmentRecord* parent() const { return m_parent; }
+
+protected:
+    explicit EnvironmentRecord(EnvironmentRecord* parent);
+    explicit EnvironmentRecord(GlobalObjectTag);
+
+    virtual void visit_edges(Visitor&) override;
+
+private:
+    EnvironmentRecord* m_parent { nullptr };
+};
+
+}